1. Field of the Invention
This invention relates to a press brake adapted to apply bending force on metal blanks in the form of a sheet or plate to bend them.
2. Description of the Prior Art
There has so far been employed a press brake of the kind specified above which comprises a die (or lower die) fitted to a bed, and a punch (or upper die) fitted to a slide or ram and which is arranged to bend a metal blank sheet or plate between the lower die and the punch when the slide is vertically moved.
In such a press brake, however, in the case where it is desired to bend a metal blank sheet or plate in a different shape, it is required to replace the lower die and the punch with ones having the shapes corresponding to the desired configuration. Therefore, the operation becomes troublesome.
Further, when a metal blank sheet or plate is bent several times in a complicated shape, the lower die and the punch are required to be replaced with corresponding ones each time. Therefore, the operation itself becomes troublesome. In particular, in the case where a large metal blank sheet or plate is bent in a complicated configuration, the metal blank sheet or plate tends to tilt on the side of the slide and strike against the operator thus hurting him, and therefore the operation itself is dangerous. Further, when a metal blank sheet or plate is clamped by means of a blank holder, there occurs a difficulty in that the blank holder must be operated or controlled in a complicated manner.